Vitamin D deficiency in prostate cancer: Prevalence in a sun-rich climate and the influence of androgen deprivation therapy.

e17096 Background: Vitamin D is essential for calcium absorption, bone health, and immune function. Despite the abundant sunlight in Southern California, vitamin D deficiency persists. It is crucial to determine whether prostate cancer patients experience a higher prevalence of deficiency as it may impact their overall health and disease management. Androgen deprivation therapy (ADT), a cornerstone of prostate cancer treatment, is known to impair bone mineral density. Understanding whether ADT also contributes to vitamin D deficiency is essential, as it could further exacerbate bone-related complications and necessitate targeted interventions. This study investigates the prevalence of vitamin D deficiency in prostate cancer patients in a sun-rich climate and evaluates the impact of ADT on vitamin D levels. Methods: A retrospective cohort study was conducted using medical records from the Chao Family Comprehensive Cancer Center. Patients diagnosed with prostate cancer between January 2014 and 2024 were included. Vitamin D deficiency was defined as serum 25(OH)D <20 ng/mL. Demographics, cancer stage, and ADT exposure were analyzed. Confounders such as supplementation, BMI, and seasonal variation were controlled for. Statistical analyses included descriptive statistics and correlation assessments. Results: Among 120 prostate cancer patients (mean age 74 ± 9.5 years), 12.5% were vitamin D deficient. Median vitamin D level was 35.4 ng/mL at time of prostate cancer diagnosis. Deficiency rates were highest among Hispanic (31.8%) and Black (33.3%) compared to Non-Hispanic White (6.9%) and Asian (7.1%) patients. Advanced-stage disease (Stage 4) had higher deficiency rates (14.7%) versus Stage 2 (10%) and Stage 3 (8%). Among metastatic cases, castration-resistant prostate cancer exhibited higher deficiency (28.6%) compared to castration-sensitive prostate cancer (21.3%). Median ADT duration was 18 months [IQR: 10-33.5 months], with similar durations across vitamin D groups: <30 ng/mL (18 [10-41]), 30-49 ng/mL (18 [8-30]), and ≥50 ng/mL (20 [14-28]). Patients with advanced-stage disease had longer ADT durations (21 [12-39]) compared to earlier stages (14 [8-20]). No significant differences in vitamin D levels were observed before and after ADT initiation (36 ± 20 vs. 38 ± 19 ng/mL; p=0.45). Seasonal variation in diagnosis, including winter (38 ± 20 vs. 42 ± 18; p=0.30) and summer (34 ± 20 vs. 34 ± 21; p=0.95), as well as older age (≥65 years) (39 ± 20 vs. 41 ± 21; p=0.70), did not significantly impact post-ADT levels. Conclusions: Vitamin D deficiency is prevalent in prostate cancer patients, particularly among racial minorities and those with advanced-stage disease. While ADT did not significantly alter vitamin D levels, findings highlight the importance of routine monitoring and supplementation. Future studies should explore long-term impacts on treatment outcomes and bone health.